The present invention relates to compositions and processes for halogenating carboxylic acids, acid halides and acid anhydrides at the .alpha.-carbon atom in the presence of a cyanoquinone compound.
The halogenation of organic compounds at a specific carbon atom (i.e., regiospecifically) is difficult, especially on an industrial scale. In general, halogenation reactions tend to occur to some extent at all available carbon-hydrogen linkages in the molecule undergoing halogenation.
Some regioselectivity in halogenation reactions has been achieved heretofore. For example, the treatment of aliphatic carboxylic acids having at least one .alpha.-hydrogen atom with halogens such as bromine or chlorine in the presence of a phosphorus halide catalyst comprises the well-known Hell-Volhard-Zelinsky preparation of .alpha.-halo acids. However, chlorination reactions carried out according to the HVZ procedure are not regiospecific and mixtures of chlorinated products are typically secured. For the most part, the HVZ halogenation is used to brominate carboxylic acids and is, therefore, expensive as compared with the corresponding chlorination reaction.
By the present invention, it has been discovered that cyanoquinone compounds can be used in the .alpha.-halogenation of carboxylic acids, carboxylic acid anhydrides and carboxylic acid halides. The resulting .alpha.-halogenated products are useful as lubricant additives and as intermediates for the production of lubricants, and as surfactants and surfactant intermediates.